Rubber compounds are notoriously difficult to analyse. The rubber may contain a variety of additives including other polymers, which are used to enhance the properties of the rubber matrix, for example, plasticisers, inorganic fillers, carbon black, antidegradants, cure systems, fire retardants and polyvinyl chloride. It is unlikely that more than 90-95 of a complex formulation can be determined by analysis alone. Compounds may contain over 15 different ingredients, some present at very low levels. During vulcanisation chemical reactions occur which may change the nature of the components in a rubber and this must be taken into account. It is evident that a good rubber analyst must have a working knowledge of rubber technology to succeed.

Rubber analysis is used for a variety of purposes such as quality control, reverse engineering (deformulation) and to determine causes of failure.

A wide variety of techniques can be used to discover different facts about a rubber compound. For example, elemental analysis may be required, or a method of measuring cure state.

Many spectroscopic techniques are employed in rubber analysis including infrared spectroscopy, ultraviolet light spectroscopy, NMR spectroscopy, atomic absorption spectroscopy, X-ray fluorescence spectroscopy, chemiluminescence spectroscopy and energy dispersive analysis. Chromatographic methods include gas chromatography-mass spectrometry (GC-MS), high performance liquid chromatography (HPLC), gel permeation chromatography (GPC) and thin layer chromatography (TLC). Thermal techniques include differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA).

This review outlines each technique used in rubber analysis and then illustrates which methods are applied to determine which facts. For example, polymer and filler identification, molecular weight determination, elemental analysis and carbon black study methods are all included.

The author has included a worked example of the deformulation of a complex rubber compound. The review also includes useful appendices on international standards, rubber nomenclature and key polymer and ingredient properties.

This text is a good introduction to a very complex subject area and will enable the reader to understand the basic concepts of rubber analysis. It is around twice the size of the normal reviews in this series.

Around 350 abstracts from the Polymer Library accompany this review, to facilitate further reading. These include core original references together with abstracts from some of the latest papers on rubber analysis.

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